It is known that during milling cutting operations the length of the cutting edge is directly related to the vibrations induced in the milling cutter and the workpiece and the energy requirements in carrying out the cutting operation. These vibrations give rise to so-called "chatter". In other words, "chatter" tends to increase with increasing length of the cutting edge.
The vibrations and consequent "chatter" arise out of the forces exerted on the cutting insert and especially on the cutting rake surface thereof by the chip which is formed and the greater the width of the chip, the greater will be the exerted forces. With a view to decreasing these vibrations and "chatter", it is known to employ milling cutters having cutting inserts with relatively short cutting edges, the inserts being so orientated with respect to the tool holder and with respect to each other that the cutting paths of the cutting edges of successive cutting inserts overlap. In this way each relatively short cutting edge gives rise to a chip of relatively narrow width, the overlap between the cutting edges of successive cutting inserts ensuring that relatively smooth milling is attained.
In practice, however, this proposal is not found to be effective, requiring as it does the careful preliminary orientation of correctly designed cutting inserts on and with respect to the tool holder.
The co-pending Application disclosed a new and improved cutting insert for use with a milling cutter, which insert is, by itself, capable of achieving the desired objective of reduced "chatter" in the use of the milling cutter tool.
There is disclosed in the co-pending Application a cutting insert for use with a military milling cutter tool and having a cutting edge defined between a cutting rake surface and a relief flank and having a base edge defined between said relief flank and a base surface;
characterized in that
said cutting edge comprises a plurality of successive component cutting edges and intermediate edges respectively located between successive component cutting edges; each component cutting edge having respective leading and trailing extremities, the trailing extremity of one component cutting edge merging with the leading extremity of a succeeding component cutting edge via an intermediate edge, said intermediate edge being directed from said trailing extremity of said one component cutting edge towards said base edge; each normal to an axis of rotation of said cutter tool which passes through a trailing extremity of one component cutting edge intersects the successive component cutting edge so that during a milling operation, successive component cutting edges overlap.
As indicated, the use of such a cutting insert in milling operations is effective in reducing undesirable vibrations and "chatter", the milled surface produced thereby tends to be undesirably serrated and this, of course, in many circumstances is undesirable.
It is therefore an object of the present invention to provide a new and improved exchangeable cutting insert for use in milling, in which the above-referred-to disadvantage is substantially reduced or overcome.